Coating method, coating apparatus and method for manufacturing component

ABSTRACT

The present disclosure provides a coating method for suppressing variations in a coating amount, a coating apparatus and a method for manufacturing a component. A coating method is employed, which includes: discharging a coating needle adhering to an adhesive from a nozzle; separating the adhesive into the tip of the coating needle and the nozzle; and adhering the adhesive to a first member. A coating apparatus is employed, which includes: a nozzle which holds the adhesive; a coating needle which is discharged from the nozzle in a state where the adhesive is adhered to the tip; and a control unit which controls moving speed of the coating needle to separate the adhesive into the tip of the coating needle and the nozzle.

TECHNICAL FIELD

The present disclosure relates to a coating method, a coating apparatusand a method for manufacturing a component. Particularly, the presentdisclosure relates to a coating method using an adhesive, a coatingapparatus and a method for manufacturing a component.

BACKGROUND

In the related art, in order to protect a pixel portion of an imagesensor, a cover glass is attached.

FIG. 1 is a perspective view of a state when a cover glass of aprotective member 6 is attached to a semiconductor element 4 of an imagesensor. In order to attach the protective member 6 to the semiconductorelement 4, initially, it is necessary to apply an adhesive 5 to asurface of the semiconductor element 4. FIG. 2 is a view showing anapparatus for applying the adhesive 5. A coating needle 1 is insertedinto a nozzle 2 which is filled with the adhesive 5.

FIG. 3 is a view of a state when the adhesive 5 is applied to thesemiconductor element 4. The coating needle 1 is moved to a bottom andcomes out from the nozzle 2. An adhesive 5 e is adhered to a tip of thecoating needle 1, and the adhesive 5 e is transferred to thesemiconductor element 4 by further lowering the coating needle 1. Thecoating needle 1 is operated at a constant speed and lowered to aposition where the adhesive 5 e is transferred to the semiconductorelement 4. When transferring, the adhesive 5 e on the tip of the coatingneedle 1 and an adhesive 5 f adhering to a lateral surface 1 f near thetip of the coating needle 1 are transferred simultaneously.

After the adhesive 5 is applied, the protective member 6 approaches thesemiconductor element 4 as shown in FIG. 1. Expanse of the adhesive 5 atthis time is illustrated in FIGS. 4A to 4C. FIGS. 4A to 4C are planviews illustrating aging variations when the protective member 6 isattached to the semiconductor element 4.

The adhesive 5 is spread in a concentric circle shape in the order ofFIG. 4A to FIG. 4C. Since the protective member 6 is transparent, theadhesive 5 can be seen.

In order to adhere firmly, it is necessary to forward the adhesive 5 tofour corners of the protective member 6. Therefore, since it isnecessary to make the adhesive 5 protrude from an external form of thesemiconductor element 4, in consideration of variations in the coatingamount, it is necessary to apply the adhesive 5 in a large amount.

Finally, FIG. 5 is a side view illustrating a finished product when thecoating amount of the adhesive 5 is too large. An adhesive dripping 11to the lateral surface of the semiconductor element 4 and an adhesivecreeping-up 10 to the cover glass occur. The adhesive dripping 11 andthe adhesive creeping-up 10 occur more often on a central part of a sideof the protective member 6. The adhesive creeping-up 10 comes into astate in which the central part of the side becomes most prevalent, anddecreases in a direction of both sides corners of the protective member6. The adhesive dripping 11 comes into a state in which the central partof the side of the semiconductor element 4 becomes most prevalent, anddecreases in a direction of both sides corners of the semiconductorelement 4. When these adhere to the protective member 6, marks appeardue to the adhesive 5 spread in a concentric circle shape, there is arisk of low quality caused by unnecessary adhesive transferring of thenext step. If coating in a large amount, in consideration of thevariations in the coating amount, it is highly possible that low qualityfinished products may be mass produced. Therefore, it is necessary tosuppress the variations in the coating amount and not to increase thecoating amount of the adhesive as much as possible.

There is a method of JP-A-2016-21736 (Patent Literature 1) as a methodfor controlling the coating amount with high accuracy. InJP-A-2016-21736, the adhesive is coated on one side of the semiconductorelement and is spread to other sides.

SUMMARY

However, JP-A-2016-21736 is not a method for suppressing variations in acoating amount and extra steps are needed.

The present disclosure solves the conventional problems and provides acoating method for suppressing variations in the coating amount, acoating apparatus and a component manufacturing method.

In order to solve the problem as described above, a coating method isemployed, in which the coating method including the following steps: adischarge step in which a coating needle adhering an adhesive comes outfrom a nozzle; a separating step in which the adhesive is separated ontothe tip of the coating needle and the nozzle; and a adhering step thatthe adhesive adheres to a first member.

A component manufacturing method is employed, in which the manufacturingmethod including the following steps: a discharge step in which acoating needle adhering an adhesive comes out from a nozzle; aseparating step that the adhesive is separated onto the tip of thecoating needle and the nozzle; a adhering step in which the adhesiveadheres to a first member; and a bonding step in which a second memberis bonded from the adhesive on the first member.

A coating apparatus is employed, in which the coating apparatusincluding: a nozzle holding an adhesive; a coating needle coming outfrom the nozzle in a state that adhesive is adhered to the tip; acontrol unit that can control separation of the adhesive from the tip ofthe coating needle and the nozzle by controlling a moving speed of thecoating needle.

According to the transferring coating apparatus of the presentdisclosure, since coating amount variations of a minute point oftransferring can be reduced, it is possible to coat accurately thecoating amount which can firmly fill up four corners under the bondingmember and to improve bonding reliability between a semiconductor chipand a bonding member. In addition, amount extruding from bonding membersbecomes fewer and influence of next steps will be eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view when a cover glass is attached to a relatedsemiconductor element;

FIG. 2 is a view illustrating adhesive coating by means of relatedadhesive coating needle;

FIG. 3 is a view illustrating a relationship between the adhesive andthe coating needle in a transfer of related adhesive coating;

FIGS. 4A to 4C are plan views when the related semiconductor elementadheres to a protective member;

FIG. 5 is a side view of a semiconductor element when a related adhesivecoating means is used;

FIG. 6A is a front view of a mounting structure of an embodiment, andFIG. 6B is a plan view of the mounting structure of the embodiment;

FIG. 7 is an enlarged side view of the semiconductor mounting structureof the embodiment;

FIG. 8 is a view illustrating a relationship between the adhesive andthe coating needle which is stopped in the adhesive coating of theembodiment;

FIG. 9 is a view illustrating a relationship between the adhesive andthe coating needle after the stop in the adhesive coating of theembodiment;

FIG. 10 is a view illustrating a relationship between the adhesive andthe coating needle which is lowered again in the adhesive coating of theembodiment;

FIG. 11 is a view illustrating a relationship between the adhesive andthe coating needle which is transferring in the adhesive coating of theembodiment;

FIG. 12A is a view illustrating an operation flow in a related adhesivecoating, and FIG. 12B is a view illustrating an operation flow in theadhesive coating of the embodiment;

FIG. 13 is a graph obtained by plotting coating amounts in the relatedmethod and the embodiment; and

FIG. 14A is a view illustrating a relationship between time and aposition of a tip of the related coating needle, FIGS. 14B and 14C areviews illustrating a relationship between time and a position of a tipof the coating needle of the embodiment.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described with referenceto the drawings.

<Structure>

FIG. 6A is a side view of a semiconductor mounting structure 100 of anembodiment, and FIG. 6B is a plan view of the semiconductor mountingstructure 100 of the embodiment. FIG. 7 is an enlarged side view of thesemiconductor mounting structure 100 of the embodiment and illustratesan end portion of an adhesive 5. In FIG. 7, a protective member 6adheres to a semiconductor element 4 by the adhesive 5.

The semiconductor element 4 is a functional element such as an imagesensor. In this example, the semiconductor element 4 is a square ofabout 1 mm×1 mm in a plan view and the overall shape thereof is arectangular parallelepiped.

In this case, the protective member 6 is a cover glass for protectingthe semiconductor element 4. The size of the protective member 6 is asquare less than 1 mm×1 mm and is smaller than the semiconductor element4 in a plan view.

The adhesive 5 is for making the semiconductor element 4 adhere to theprotective member 6.

The adhesive 5 includes a center portion 5 c between the semiconductorelement 4 and the protective member 6, a periphery portion 5 b locatedon the periphery of the center portion 5 c and a lateral surface portion5 a creeping up to the lateral surface of the quadrate protective member6. Further, the center portion 5 c is only located on the bottom(bonding surface) of the protective member 6. The lateral surfaceportion 5 a is located on the top of the periphery portion 5 b. Thelateral surface portion 5 a and the periphery portion 5 b change greatlydepending on variations in the coating amount of the adhesive 5. Sincean amount that can completely fill at least the center portion 5 c needsto be served as a minimum coating amount, it is necessary to aim formore than an amount that can be minimum depending on the variations inthe coating amount. As a result, when variations in the coating amountare large, there is an amount that is more than the lateral surfaceportion 5 a and the periphery portion 5 b need, which may cause anadhesive dripping 11 to the lateral surface of the semiconductor element4.

The semiconductor mounting structure 100 of the embodiment can reducethe variations in the coating amount of adhesive 5 and can reduce theoccurrence of the adhesive dripping 11 to the lateral surface of thesemiconductor element 4.

This structure can be realized by the following manufacturing method.

<Manufacturing Method>

In a related art, a method for applying the adhesive 5 by controlling acoating needle 1 from starting lowering to transferring at a constantspeed is used. Here, a region of the constant speed excludes regions oflow speed at initial stage when the coating needle 1 starts to move andan end stage when the coating needle 1 is stopped.

In an embodiment, variations in the coating amount of adhesive 5 can bereduced by controlling a speed of a lowering operation of the coatingneedle 1.

<Steps>

FIG. 12A shows a related adhesive coating operation, and FIG. 12B showsan adhesive coating operation of the embodiment. Compared to the relatedmethod, in the embodiment, the moving speed of the coating needle 1 iscontrolled to be changed and temporarily stopped.

Then, an operation of temporarily stopping the operation of lowering thecoating needle 1 is used and steps until applying the adhesive 5 to thesemiconductor element 4 will be described.

(1) Filling Step

Firstly, the adhesive 5 is filled into a nozzle 2 and is held. In thisexample, an acrylic resin type adhesive having a low viscosity of about1000 mPa·s was used as the adhesive 5. FIG. 2 is a view of an apparatusapplied with the adhesive 5. The coating needle 1 is inserted into thenozzle 2 which is filled with the adhesive 5. If the adhesive 5 isalready held to the nozzle 2, the filling step is not necessary.

(2) Discharging Step

From a state of FIG. 2, the coating needle 1 is moved downward and thecoating needle 1 is discharged to the outside of the nozzle 2.

(3) Separating Step

After the discharge step, a constant moving speed of the coating needle1 is changed and stopped halfway. FIG. 8 is a view illustrating arelationship between the adhesive 5 and the coating needle 1 which isstopped halfway. The coating needle 1 is moved in a downward directionand is temporarily stopped when the coating needle 1 protrudes aconstant distance from the nozzle 2. The adhesive 5 extruded from thenozzle 2 is separated into an adhesive 5 e adhering to a tip of thecoating needle 1 and an adhesive 5 d adhering to a lateral surface ofthe coating needle 1. The adhesive 5 is separated by stopping. Further,although the adhesive 5 can be separated even if the coating needle 1 ismoved at the constant speed, the position of separation is almost notchanged.

At this time, the coating needle 1 is stopped when protruding 1 mm fromthe tip of the nozzle 2. The length of the coating needle 1 protrudingfrom the tip of the nozzle 2 needs to be changed according to the typeof the adhesive 5, the outer diameter and the inner diameter of thenozzle 2, and the outer diameter of the coating needle 1.

FIG. 9 is a view illustrating a relationship between the adhesive 5 andthe coating needle 1 after the stop in the adhesive coating of theembodiment. FIG. 9 shows a state 1 second later after the coating needle1 is stopped. The adhesive 5 e adhering to a tip surface (a bottomsurface) of the coating needle 1 is same as that shown in FIG. 8 (thecoating needle 1 is held as in FIG. 8), but the shape of the adhesive 5d adhering to the lateral surface of the coating needle 1 is different.The adhesive 5 d adhering to the lateral surface of the coating needle 1is changed by being separated and pulled back to the nozzle 2 by arepellent force extruded to the coating needle 1 due to viscosity of theadhesive 5. As a result, the adhesive 5 d does not adhere to a lateralsurface if near the tip of the coating needle 1.

(4) Coating Step

After the separating step, the coating needle 1 is moved again. FIG. 10is a view illustrating a relationship between the adhesive and thecoating needle 1 which is lowered again in the adhesive coating of theembodiment. Even if the coating needle 1 is lowered again, the operationis continued in a state in which the adhesive 5 d does not adhere to thelateral surface if near the tip of the coating needle 1.

FIG. 11 is a view illustrating a relationship between the adhesive 5 andthe coating needle 1 which is transferring in the adhesive coating ofthe embodiment. In the adhesive coating to the semiconductor element 4,only the adhesive at the tip of the coating needle 1 is transferred.Since the adhesive 5 d adhering to the lateral surface of the coatingneedle 1 is not subjected to transfer, the variations of the amount ofthe coated adhesive 5 is stable with little variation.

Time of the temporary stop is preferably in a range of 0.5 second to 5seconds. Although the time can be longer, when considering productivity,5 seconds or less are preferable.

When a place to stop, a place to reduce the speed of the coating needle1, or a place of the separating step is 1 mm to 2 mm and less than 3 mmaway from the nozzle 2. If the distance from the nozzle 2 is too long(longer than 3 mm), the adhesive 5 which cannot be drawn in and out of anozzle 2 side stays on a side of the coating needle 1, and the coatingamount will not be stable.

Even if the nozzle needle 1 is not temporarily stopped, the same effectcan be expected by reducing the speed from a certain point. FIG. 14A isa view illustrating a relationship between time and a position of thetip of the related coating needle. FIGS. 14B to 14C are viewsillustrating a relationship between time and a position of the tip ofthe coating needle of the embodiment. In FIG. 14B, the coating needle 1is stopped halfway. In FIG. 14C, the coating needle 1 is not stopped butthe speed is reduced halfway. For example, even if the coating needle 1is discharged from the nozzle 2 at a speed of 1 mm/second, proceeds for5 seconds at a speed of 0.11 mm/second from the position 1 mm away fromthe nozzle 2, and then is moved at a speed of 1 mm/second, the result issimilar to the case of the temporary stop. It is preferably to changethe moving speed stepwise halfway. Stopping or speed reducing may onlyoccur in one position. Compared to changing gently as a whole, adiscontinuous change is preferable.

Further, reducing the speed of the coating needle 1 (to stop the coatingneedle 1 at one end) excludes the initial stage and the end stage. Thatis, the initial stage immediately after the coating needle 1 isprotruded from the nozzle 2 and the end stage before and after thecoating needle 1 approaches the semiconductor element 4 of an object andapplies the adhesive 5 are excluded.

(5) Bonding Step

After the adhesive 5 is applied, the semiconductor element 4 and theprotective member 6 are united. Thereafter, the adhesive 5 is cured.

<Experiment>

FIG. 13 shows a result of plotting a graph obtained by applying theadhesives and plotting coating amounts in the related method and theembodiment. The experiment is performed under the following conditions.

Adhesive: acrylic resin-based about 1000 mPa·s

Inner diameter of nozzle: ϕ 800 μm

Speed of coating needle: 1.75 mm/second

Diameter of coating needle: ϕ 400 μm

Temporarily stopping position: a position of protruding 1 mm from anozzle

Temporarily stopping time: 1 second

Except that the coating needle is not temporarily stopped in the relatedmethod, other conditions are the same.

Since the variations in the coating amount can be significantly reduced,compared to 3σ=0.22 in the related method, 3σ becomes 0.06 in theembodiment. At least, in the embodiment of this time, 3σ becomes 0.20 orless. More preferably, 3σ becomes 0.10 or less.

Compared to the coating method by means of transferring by the relatedcoating needle, by temporarily stopping the lowering operation of thecoating needle as described above, it is possible to eliminate theadhesion of the adhesive to the lateral surface of the coating needleand to reduce the variations in the coating amount.

(As A Whole)

An adhesive widely includes solder paste and a bonding member.

Instead of the semiconductor element 4, as a first member, it is alsopossible to apply the first member to various kinds of devices. Insteadof the protective member 6, except for the cover glass, other devices asa second member can also use various kinds of protective members.

A control such as a control of the coating needle 1 in the apparatus canbe performed by a control unit 12 of FIG. 3.

The coating apparatus of the present disclosure has a feature ofreducing variations in the coating amount during one point transferringand can be applied widely to applications where members are attachedtogether with high quality. In addition, the semiconductor mountingmethod and the semiconductor mounting apparatus of the presentdisclosure are not limited to a semiconductor and can be used inprecision components such as optical components.

What is claimed is:
 1. A coating method comprising: discharging acoating needle with an adhesive attached as one lump from a tip to alateral surface of the coating needle from a nozzle; separating the onelump of adhesive into adhesive at the tip of the coating needle andadhesive at the lateral surface of the coating needle by furtherdischarging the coating needle after the discharging and changing amoving speed of the coating needle; and making the adhesive at the tipof the coating needle adhere to a first member by further dischargingthe coating needle after the separating, wherein the changing of themoving speed of the coating needle includes a temporary stop.
 2. Thecoating method according to claim 1, wherein, in the separating step,the adhesive at the lateral surface of the coating needle returns to aside of the nozzle and the adhesive at a tip surface of the tip of thecoating needle is maintained.
 3. The coating method according to claim1, wherein the separating step is performed at a distance of 1 mm ormore and less than 3 mm away from the nozzle.
 4. The coating methodaccording to claim 1, wherein time of the temporary stop is 0.5 secondor more and 5 seconds or less.
 5. The coating method according to claim1, wherein when the coating method is repeatedly performed, 3σ of avariation in an amount of the adhesive adhering to the first member is0.20 or less.
 6. A method for manufacturing a component, the methodcomprising: the coating method according to claim 1; and bonding asecond member to the first member with the adhesive on the first member.7. The coating method according to claim 1, wherein in the making of theadhesive, the adhesive at the tip of the coating needle is attached tothe first member in a state where the one lump of adhesive is separatedinto the adhesive at the tip of the coating needle and the adhesive atthe lateral surface of the coating needle.